Mac OS X is the only major consumer operating system that comes complete with a fully configured and ready-to-use Java runtime and development environment. Professional Java developers are increasingly turning to the feature-rich Mac OS X as the operating system of choice for both Mac-based and cross-platform Java development projects. Mac OS X includes the full version of J2SE 1.5, pre-installed with the Java Development Kit (JDK) and the HotSpot virtual machine (VM), so you don't have to download, install, or configure anything.